Refrigerating apparatus and method



Nov. 15, 1932. J w -rm, JR 1,887,693

REFRIGERATING APPARATUS AND METHOD Original Filed June 15. 1926 2Sheets-Sheet 2 I j V If INVENTOR kfamf WMarJzhL/Z' aw/gr;

ATTORNEY Patented Nov. 15, 1932 UNITED STATES PATENT OFFICE JAMES W.MARTIN, JB., OF YONKERS, NEW YORK, ASSIGNOR T DRiYICE EQUIPIEN'I.CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE REFBIGERATING APPARATUS AND METHOD Original application filed June 15, 1926,

lems presented by attempts to employ solid carbon dioxide for ordinarycommercial refrigerating purposes. Commercially, solid carbon dioxide inrelatively dense form is made either by freezing the liquid directly tothe solid blocks or by expanding the liquid to so-called snow, which isthen compressed into blocks of desired density. Among the unique factorsinvolved in the use of such refrigerant are the following:

(1) The solid carbon dioxide melts or rather sublimates directly to agas, without any intermediate state.

(2) The volume of the gas evolved is approximately 500 times the volumeof the block, normally about 8 cubic feet per pound of the solid carbondioxide, that is, where the block has a density-or about pounds percubic foot. I

(3) The temperature of the Sublimated gas 0 while nominally,approximately 114 F. be-

low zero, ma vary within wide limits. aboveand below 1; is temperature,which maybe roughly indicated as somewhere between 85 F. and 140 F.

i (at) This wide variation of temperature is the result of anaccelerated or retarded sublimating rate, and while the temperaturevariation so caused is of utility and importance in my presentinvention, the accelera- 0 tion and retarding of the sublimating rateand,the factors controlling the same are of even greater importance.

(5) In considering these, heat insulation may be disregarded because itis well understood that the sublimating rate will be Serial No. 116,103.Divided and em application filed limit 21, 19:30. Serial No. 437,652.

greater or less according as the heat insulation is greater or less.

(6) The present problems concern the active or dynamic factors .ofsublimating rate, which are:

(a) Convection of the heat by circulation of the air or gas within therefrigerated space;

(6) The enormously variable insulation afforded by the atmosphere withinsaid space according as it iscomprised mainly .of the carbon dioxide gasor'mainly of air.

, (7) The unique factor in the control of accelerated or retardedmelting rate is what is known as partial pressure. In an atmosphere ofpure carbon dioxide gas, the rate of evaporation is minimized and thecorresponding temperature of the gas may approximate the upper limit,whereas in a constantly maintained atmosphere of pure air, the meltingrate is greatly accelerated and the temperature of the gas approachesthe lower limit. That is to say, pure air has an eifect similar to thatofa perfect vacuum in accelerating the'melting rate and any percentageadmixture of airin a carbon dioxide 7 atmosphere has an effect similarto that of-a corresponding partial vacuum. I

-' As related-to the practical problems of my present-invention, theobject is to maintain a relatively pure atmosphere of'earbon dioxidegas, for the double purpose of retarding evaporation rate andmaintaining high insulating value. This is accomplished by properlycontrolling the flow of the great volumes of gas per unit of solid thatis evaporated, while at the same time gradually and difiusely applyingrefrigerated values of the fresh gas by conduction, to modify thetemperature of the gas and prevent over-refrigeration upon dischargethereof into the refrigerated space;

One object of my invention is to establish a. heat absorbing circuit ofapproximately pure gas, affording maximum insulation, a jacent exteriorwalls -of the refrigerated space. A special feature is the arrangementof the heat absorbing and insulating circuit of said approximately puregas to serially include a down-leg of circulation of the gas evaporatedfrom the solid carbon dioxide, terminating in an up-leg incounterbalancing relation so that the down and up circuit functions as aheat absorbing thermostat. While the up-leg may discharge into the outerair, as in one special form of my apparatus, it preferably dischargesinto the refrigerated space upon escaping from the thermostatic circuit;being relatively pure gas it flows down. to the bottom of said space,displacing the air upward. The 500 volumes of gas per unit solid of theabove density are thus most eficiently employed to expel air from thetop of the refrigerated space. Obviously, evaporation of acubic foot ofsuch solid would wash out a refrigerated space 2 X3 X4, twenty-five orthirty times during the evaporation period.

, An important practical point is that commercial refrigeratingapparatus of all kinds is very apt to have leaks whereby. the pure gas,being very heavy, is apt to drain out and unless the melting rategreatly exceeds the leaking rate, air will be drawn in at the higherlevel leaks. Any such inleak of air, even a small percentage, has aremarkable effect in decreasing the insulation value of the gas, but inthe preferred form of my invention, this is compensated for by the phenomenal acceleration of gas evolution proportional to the percentage ofair in the refrigerated space. This is one of the reasons why there arecertain advantages in having the gas overflowing from the up-leg of thecirculation discharge into the refrigerated space, thereby tending toforce air into the top of the s ace containing the solid carbon dioxide.T us, under emergency conditions, the greater the amount of therelatively light, relatively non-insulating air, the more rapldlg willgas be evolved to drive out that air.

y the above and other pro er methods of utilizing the above describedactors of commercial refrigeration of solid carbon dioxide,

it has been demonstrated that the solid carbon dioxide, though havingless than twice the refrigerant value of water ice, may be made toafford from ten to twenty or more times the refrigerating efliciency ofthe latter.

From the above it will be understood thatmy invention involves certainadvantages never before attained in connection with carbon dioxide.refrigeration as concerns modi fying the temperature of the gas andapply ing its refrigerant value in such a way as to minimize danger ofover-refrigeration of food and similar products within the refrigerator.Preferably, the carbon dioxide refrigerant is in a compartment in thetop of the refrigerator, whence the heavy gas flows downward in acentral conduit entirely within the refrigerated space. This downflowpath is preferably the interspace between the walls of a centralpartition, which preferably extends from front to rear of therefrigerator and down to a bottom space, through which the gas flowslaterally to and up through draft passages between the outerrefrigerator shell, and the inner shell which encloses the refrigeratedspace. When the gas reaches the top of this interspace, it spills freelyover into the food-containing body portion of the refrigerator, where itnaturally settles downward through all of the compartments toward thebottom thereof, displacing warmer carbon dioxide or air upward. In thisway, the inner metal shell is refrigerated by the primary downflow inthe central partition and then is both refrigerated and heat-insulatedby the countercurrent flow of gas in the exterior interspace between theinner shell and the exterior refrigerator casing. Theprimary downflowthroughthe central partition takes effect entirely within and surroundedby the refrigerated space, while the flow across the bottom and up thesides and back operates to re- 9.,

While the upper compartment containing the solid carbon dioxide may beclosed so that the above described circulation is forced by the pressureof the generated gas, the more specific claims of my present applicationcontemplate leaving both the entrance and exit of the flow circuitvented to atmosphere within the refrigerator so that the circulationwill be mainly static, that is to say, the gas is left free to spillover the top of the refrigerant chamber, but it does not do so becausethe down-column being not urally colder and more dense than the upcolumnwill establish an unbalanced condition whereby the gas will be forcedout from the top of the upflow column, until said upflow column becomesas cold as the downflow column. Moreover, the quantity of the flow bevented or entirely open. Moreover, when the above described thermostaticcirculation is active, as, with such percentage of air as has not eenexpelled from the top of the refrigerator, may be drawn downward intothe solid carbon dioxide compartment, thereby accelerating the meltingof the solid until the circulation is automatically checked by loweringtemperature and by the increasing percentage of carbon dioxide gas,thereby increasing density of the up-column.

In actual practice, I find this automatic thermostaticcontrol is soperfect that desired temperatures, above freezing, may be main tained inthe ordinary domestic refrigerator merely by predetermining the amountand gas-tightness of paper, pasteboard or other insulating wrappings forthe solid carbon dioxide or for the walls of the refrigerant box. Inthis way, I have very satisfactorily operated a domestic refrigeratornormally requiring 7 5 pounds of water ice per day on 8 pounds of-solidcarbon dioxide per day.

Considering the counterbalancing downfiow and upfiow 'columns as anautomatic self-controlling thermostatic instrument, it will be evidentthat further and more accurate adjustment for given ranges oftemperature may be had bymaking the upflow col: umn somewhat shorterthan the downfiow column, and it is even possible to make the upflowcolumn somewhat higher than the downflow column, so that the gas willspill from the top of the upflow column only when the latter is verymuch warmer than the downflow column.

If design of the areas and cross-sections in combination with insulationis insutlicient to secure a high enough maximum speed of circulation,prefer to employ valves either in the down-column or theycross-connection or the rip-column, controlled manually or by well knownthermostatic elements, such as bimetallic strips or metallic bellowstubes. The natural self-regulating quality of the counterbalancedcolumns may thus be subject. to

arbitrary control.

When thermostats are used, the sublimat ing rate of the solid may becontrolled and determined, according to a fundamentally new method:

The upper part of the down-column containing the solid carbon dioxide isheavily in sulated, but the solid therein is entirely uninsulated and athermostatic valve is arranged to control downflow of the cold gas fromthe refrigerant in the down-column either by cutting it off entirely orlimiting it to a small predetermined minimum. In this situation, theinsulated walls plus the cold carbon dioxide remaining in the box andoperating as effective insulating for the solid, willnormally minimizemelting,but whenever the thermostatic valve is open, this extremely heagas will fall rapidly in the down-column, rawing air into the top of therefri erant box. I have discovered that such part1al or completesubstitution of air for carbon dioxide in contact with the solid has theremarkable effect of lowering its sublimating point from say 110 F. to130 or 140 F. and in this change in temperature a very considerableamount of carbon dioxide is evaporated.

This plus the sensible heat of the air may increase the evaporation ratefrom say 5%'or 10% up to say, 40% or per 24 hours.

I believe I am the first to utilize and effectively control air, as afactor in determining the rate of melting of solid carbon dioxide, andparticularly to eliminate this factor to any desired extent bypredetermining the amount and gas-tightness of paper, pasteboard orother insulating wrappings for the solid carbon dioxide, therebyprotecting it from actual contact with the circulating gasair mixtures.

While the arrangement of the down-flow column as a central partition inthe refrigerator with two counter-balancing upflow columns in the outerwalls, is a desirable arrangement, I find that it is entirelypracticable to have only 'two columns, the downflow column being anouter wall of the refrigerator, the same as the upflow'column.

While the above system may be built into a refrigerator, an importantpractical-feature 1 of my invention as disclosed herein is itsadaptability for handy and inexpensive application to the interiors ofordinary ice refregerators. F or such purposes, the downcolumn withrefrigerant box at the top thereof may be constructed in one piece,fitted against one side of the refrigerator chamber, and the up-columnin another piece, fitting against the other side with a cross-connectionin the bottom in the form of ordinary piping with detachable coupling.

The above and other features of my invention will be more evident fromthe following description in connection with the accompanying drawings,in which Figs. 1 and 2 are sections showing my invention as applied to arefrigerator ofthe domestic type, Fig. 1 being a vertical section on theline 1-1, Fig. 2, and, Fig. 2 a horizontal section on the line 2-2, Fig.1;"

Fig. 3 is a perspective view showing a modified form of apparatus forthe practice of my invention, adapted to be fitted into a domesticrefrigerator of ordinary type;

Figs. 4, 5 and Gare diagrammatic views of other modifications showingthe paths of flow of the carbon dioxide gas and various points at whichthermostatically controlled valves may be applied; and

Figs.'7 and 8 are conventional views showing solid carbon dioxide asenclosed, respectively, in pasteboard and paper wrappings af-z fording apredetermined amount and gastightness for protection of the solid carbondioxide.

In Figs. 1 and 2, a domestic refrigerator of the upright type isconventionally indicated as comprising a box-like structure, 1, thewalls of which are of any suitable heat insulating construction, havingin the front face thereof upper doors, 2,-2, middle doors, 2a, 2a, andlower doors, 27), 2b. In order to adapt such a box for operation inaccordance with my present method, it is only necessary to fit therein alining structure which may be of sheet metal, and sufficiently smallerthan the interior of the box of.the refrigerator, to leave the requiredupfiow passages between said lining and the interior walls of said box.The lining structures may comprise a bottom, 3, resting on suitablesupporting blocks, 4, parallel with the fioor, a back, 5, parallel withthe back of the refrigerator and sides, 6, 6, parallel with the sides ofthe refrigerator, with a central partition comprising spaced apartwalls, 7, 7 providing a downfiow passage, 8, leading from a solid carbondioxide container, 9, which latter is preferably protected by wood orother insulating material, 10, in which the solid may be supported onblocks 11. The refrigerator may have a close ly fitting removablesection, 13, through which solid may be charged into the refrig erantbox. The front edgesof the side and bottom walls are preferably fittedair-tight v against the front of the refrigerator, as

shown, so that the bottom, side and back interspaces will be practicallytight. The down passage, 8, between the partition walls, 7, 7, is ofcourse closed in both front and back, as is also the refrigerantcontainer, 9. The operation of this arrangement shown in Figs. 1 and 2will be evident from the drawings. The closure, 13, being removed, theblock of solid carbon dioxide will be charged into the refrigerant box,9, and the cover 13 closed. The article or materials to be refrigerated,

. specifically food products, will be placed upon shelves, 141:, 14,resting on suitable ledges, 15, 15; The solid carbon dioxide having anextremely low melting point, or rather, sublimating point, approximately110 R, will absorb heat from its surroundings and will gasify. The gaswill circulate in the paths shown by the arrows, gravitating through thedown passage, 8, flowing laterally and rearwardly at the bottom, thenupward in the interspaces, 8a, 8b, and So, at the sides and back,ultimately flowing over the upper edge of the side walls, 4, and backwall, 5,

into the refrigerating space where the perishable products are stored.The dry gas in the refrigerant box, 9, will speedily displace all airand the remarkable insulating effect of.

said gas will then be available to retard conduction or convectionof'the heat from the walls, 9, to the refrigerant. In larger boxes, suchas are to be entered by the operator, the

shown in Fig. 5.

As before described, the warmer the gas is in the lip-passages, 8a, 8b,80, the more rapid will be the gravity downfiow of the colder gas in 8.This gravity flow will tend to create a slight suction at the top of therefrigerant box, 9, and air will flow in at 12, 12, from the relativelywarm refrigerator spaces, which may be approximately 35 above zero asagainst 110 below zero at which the solid evaporates. As explainedabove, very small amounts of such air will effectively accelerateevaporation of the refrigerant besides lowering the temperature, therebygreatly augmenting the supply of refrigerant flowing downward in 8.Obviously, however, such rapid flow of the cold fluid intotheup-passages will speedily bring the temperature down and the weight upmore nearly to the temperature and weight of the gas in downcolumn 8,thus automatically checking the circulation and permitting therefrigerant box, 9, to refill itself with pure carbon dioxide, withresulting great increase of insulation of the solid.

produce gas'evolution only by heat absorp-- tion, by and in accordancewith the temperature of the circulating atmosphere. This is because thepaper or pasteboard wrappings preservethe solid carbon dioxide in anatmosphere. of the pure gas evolved within the wrappings and, therebeing no actual contact between the atmosphere and the solid, there canbe none of the peculiar accelerating action on the evaporation which isdescribed elsewhere. lVhile such accelerating action, proportional tothe percentage of air in the circulation, is often highly desirable,particularly in a domestic refrigerator, it will be obvious that saidpercentage of air does not always or necessarily vary with thetemperature within the refrigerator. Consequently, where the wrappingsare used the gas evolution will be responsive solely to the temperatureof the circulating atmosphere, and independent of What percentage of airit may have accidentally picked up. Simple conventional forms of theabove described paper and pasteboard wrappings are shown in Figs. 8 and7 respectively, an ordinary paper bag with its mouth folded over beingbox being shown in Fig. 7. More perfect gas-tightness with somewhat lessheat insuj lating quality will result, where the material of the box issheet metal. In all cases, the insulating effect will be largely due tothe pure dry cold gas which is thus retained as an insulating blanketaround the solid carbon dioxide.

These qualities and functionings, dependent on the amount andgas-tightness of insulation in which the solid carbon dioxide isenclosed, may of course be utilized in any of the circulatory systemsillustrated herein. Moreover, they have been made the basis of aspecifically different apparatus and method set forth in my copendingapplication Ser. No. 235,044, filed November 22nd, 1927.

While the counterbalance of the up-column of gas against the down-columnthus affords very effective thermostatic control of a closely graduatedsort, much sharper control may be had by arranging a valve, 17, topartially or wholly close or open the downfiow passage, 8. Such valvemay be operated by hand or, as diagrammatically indicated in thedrawings, by means of a thermostat, 18, of the well known metallicbellows type.

In the use of the refrigerator for ordinary household purposes, any oneof the doors, 2, 2a, 2?), may be opened at any time. If an upper door,2, is opened, only the carbon dioxide above the lower edge of, that dooropening can spill out and with the central partition as shown, only thegas on one side of the partition will spill. If the middle door, 2, isopen, the corresponding compartment may be drained and if left open longenough, some, or even inost, of the gas may leak out from thecompartment above it. Similarly if a lower door, 25, is opened, itscompartment and also the middle and upper compartments above the samemay also be drained. Drainage of upper compartments through lower doorsmay be minimized, however, by making the shelves of sheet metal,substantially fitting the cross-section of the chamber, their frontedges fitting as closely as practicable the doors, in addition to thefit at the sides and edges.

Under all these conditions, and even if all of the doors be opened andthe entire refrig-- erating space is drained, it is still impossible tounduly warm up the side and .back

walls, 4, 5, or the partition wall, 7, and there will be at all times asubstantial volume of cold gas in contact therewith ready to reduce themimmediately to standard low temperature, the instant the doors areclosed and the walls can again work on a single body of confinedatmosphere. Thereupon the refilling of the refrigerating space withcarbon dioxide will proceed at a pace which will be accelerated inproportion to the amount of heat that was permited to enter therefrigerating space while the doors were open.

It should be clearly understood that reeoolin by discharge of coldcarbon dioxide into t 1e refrigerating space to expel the warm air isfar quicker and more effective than any method whatever that depends onabstracting heat from said air instead of expelling'it.

A much simpler arrangement adapted for application to almost anyrefrigerant box of any size or shape is indicated in F i 3. Here theback wall of the interlining an the crossflow beneath the floor are botheliminated, the refrigerating surfaces being limited to the sides of thespace to be refrlge'rated, the apparatus comprising a sheet metalconstruction embodying the refrigerant box, 9a, and a thin, deep boxmember, 8w, the latter affording the downfiow passage for the gasevaporated in the box 9. A corresponding flat box, 8y, of the same facearea as 8a, 9a, is connected therewith by the bottom cross-flow pipe 20.This connection is made detachable by employing an ordinary pipecoupling, 21. The member 82:, is fitted against one interior side wallof the refrigerator and 831 against the opposite wall. The pipe 20 willbe of suitable length to hold them against their respective walls. JVhen in position, the parts are connected for operation by screwing upcoupling 21. The upright members are held against their respectivewalls, by pipe 20, acting as a distance rod, and at a higher levelshelves on the ledges 22 serve the same function. Additional securingmeans may be employed if desired. As shown, the top of the refrigerantbox, 9a, and also the top of the member, 8.9:, are both shown as open topermit the above described thermo circulation. If it is desired to havethermostatic control other than the inherent thermo counterbalancedescribed above, a thermostat may be applied as shown in Fig. 1, at theoutlet of the refrigerant box or, as diagrammatically indicated at 17a,18a, in Fig. 4, at the outlet of the lip-column, or, as shown at 17b,18b, in Fig. 5, in the cross-connection between the columns. When thelatter is desired for the arrangement shown in Fig. 3, a valvecontrolled by a thermostat may be inserted at the point where thecoupling 21 is shown.

A specifically different method of thermo static control, which hascertain advantages,

ing gas and evaporation is reduced to a minior air into the up-leg 8%.

In referring to the above arrangements as mum. In this situation, thecirculation is so very slow that the up-column, 8y, may be- 00 e verywarm without having any tendency to accelerate down circulation in 854:,because 8w is in eflect a barometric column sealed at the bottom by aU-bend of the conduit. Hence, the pressure difierential takes effectmerely as a suction on closed valve 1700, at the upper end of saidbarometric column. In this situation, opening of valve 17m bythermostat, 18w, permits all the accumulated differential to operateinstantly, the suction drawing in warm. air through 9c to rapidly meltthe solid carbon dioxide, and the accumulated cold gas flowing withcorresponding rapidity downward through 8m, across and up through 8y,the other leg or the ll, and from the top of 83 it flows down into therefrigerating space,

From. the above, it will be evident that the preferred forms of myapparatus include a (ll-conduit arrangement ailording counterbalancingcolumns of the carbon dioxide gas; that the refrigerant gas evolutionbeing in one of said legs, preferably but not necessarily localized atthe top thereof, there is a perpetual tendency of the column in saidgenerator leg to overhalance the other column and cause outflow at theupper end thereof, even though the upper ends of both legs may be at thesame level and both open to atmossphere. Furthermore, the bottom of theU- bend is lilre a water-sealed plumbers trap in that the heavy gassettlingthereto by gravity .7 from the generator leg, operates as aheavier fluid seal to prevent reverse flow or hubhling back of warmedgas or air from the other leg. Hence, the generator leg ischaracteristically a downfiow leg discharging through the other legwhich is therefore characteristically an uptlow leg; and when the upperend of said generator leg is sealed as in Fig. 6, a substantialbelow-atmosphere condition may be then maintained, because of the heavygas seal in the bottom of the U-conduit.

It will be evident that a very short lip-leg" 8y, that is a J-shapedarrangement, would.

be efiective for sealing the apparatus against reverse flow or bubblingback of lighter gas U-type and J-type, it will be evident the relativecross-sectional areas of the legs and of the lateralconnection betweenthem are disregarded because it is a fundamental principle of fluidsthat the gravity pressures with resulting counter-balances ordifierentials between communicating columns, depend upon the verticalheights of the columns and specific gravities of fluid in said columns.Hence inherent thermo-counterbalance control in Fig. '1 is the same inkind as in Fig. 3, although in Fig. 1 the horizontal cross-sectionalarea of the up-leg extending around three walls of the refrigerator maybe approximate-- 1y 4 times the cross-section of the down-leg 8, whereasin Fig. 3 these areas are approximately the same. The difference is,therefore, one of degree, the much greaterheat absorbing surface ofup-leg in Fig. 1 tending to keep the gas column in that legproportionally warmer and therefore of less specific gravity.

From the above explanation of the broad Y principles of my method, itwill be evident that it may be utilized in various specific forms ofapparatus disclosing a vast number of specific variations as tohorizontal sectional areas of the columnsyconductivities and radiatingrates of the upflow column, as determined by the materials of the walls.thereof or the degree of insulation of said materials; and as tolocation and-relative arrangement of the refrigerant containing box, thedown-column and the up-column, each with reference to the other. Ingeneral, decrease of heat absorbing capacity of the down-column in anyof the known ways, as by small cross-section or cylindrical crosssectionor insulation will tend to great weight and low specific gravity of thedown-column, and consequently to a lower temperature of the upflow oractively heat absorbing column, while great heat absorbing'capacity forthe up-column, as by highly conducting walls of great area as comparedwith the flow section, will promote activity of circulation. As aspecific illustration, this principle would contemplate employing a pipeconnection, likethe pipe 21 in Fig. 3, extending upward so as toconstitute the downfiow column, as well as the cross-flow column. Such apipe could be used in place of the partition conduit 8 in Fig. 1. Aunitary generator and radiator unit may mnsist of a down-leg tank suchas shown in Fig. l, protected on one or more sides ice or completelysurrounded by insulation w and said insulation may consist partly orwholly of an upfiow leg. In Figs. 1 and 2, the upflow space, 80, at therear, may be omitted or may be partitioned from spaces 8a, 8?), thusmaking the latter two separate upflow legs each independently responsiveto different heat conditionsin the spaces on the respective oppositesides of partition 7, 7. In general, there may be as many separateorparallel connected up-legs and down-legs as may be desired.

- In'Fig. 6 I have diagrammatically indicated two upfiow columnsoperating in parallel from the same source of carbon'dioxide gas.Moreover, each of the lip-conduits, 8y, is provided with atelescopingextension, 82, whereilao to the same level or to different levels,either I above or below the level of the top of the refrigerantcontainer.

I claim: 1; The method of control of evaporation of solidified carbondioxide which includes causing it to evaporate in a container the top ofrefrigerated space, draining the resultant gas to form a down-flowstatic column and to form an uptlow counterbalancing column, and varyingthe height of the latter with reference to the height of' the containerand downflow column, for the purpose described.

2. In combination, a receptacle comprising a chamber to be cooled, acontainer in the upper portion thereof enclosing solidified carbondioxide protected by relatively gas-tight paper or pasteboard wrapping,a downflow conduit from said container in heat exchange relation withsaid chamber, and an outlet conduit connected to said downflow conduitand extending upwardly, said conduits coopcrating to control circulationof generated carbon dioxide gas.

3. In combination, a receptacle comprising a chamber to be cooled, acontainer in the upper portion thereof enclosing solidified carbondioxide protected by relatively gas-tight paper or pasteboard wrapping,a downflow conduit from said container in heat exchange relation withsaid chamber, and an outlet conduit connected to said downflow conduitand extending upwardly, said conduits cooperating to control circulationof generated car: bon dioxide gas, one of ,said conduits constituting awall of the chamber.

4. In combination, a receptacle comprising a chamber to be cooled, acontainerin the upper portion thereof enclosing solidified carbondioxide protected by relatively gastight paper or pasteboard wrapping, adown- 4 flow conduit from said conta ner, in heat exchange relation withsaid chamber, and an outlet conduit connected to said downflow conduitand extending upwardly, said conduits cooperating to control circulationof generated carbon dioxide gas, said conduits constituting wallsofsthe' chamber.

5. In combination, a receptacle comprlsing a chamber to be cooled, a.container in the upper portion thereof enclosing solidified carbondioxide protected by relatively gastight paper or pasteboard wrapping, adownflow conduit from said container in heat exchange relation with saidchamber, and' an outlet conduit connected to said downflow conduit andextending upwardly, said conduitscooperating to control circulation ofgenerated carbon dioxide gas, and the upwardly extending outlet conduitbeing formed and provided with means for varying the height of its gasoverflow outlet.

6. In combination, a receptacle comprising a chamber to be cooled, acontainer in the upper portion thereof enclosing solidified car bondioxide, 9, downflow conduit from said container in heat exchangerelationwith said chamber, and an outlet conduit connected to saiddownflow conduit and extending upwardly, said conduit v cooperating tocon trol circulation of generated carbon dioxide height between theoutlet of the upwardly extending conduit and the inlet of the containerfor the solidified carbon dioxide.

7 In combination, a receptacle comprising a chamber to be cooled, acontainer in the upper portion thereof enclosing solidified carbondioxide, a downflow conduit from said container and a plurality ofupwardly-extending, spaced-apart outlet conduits connected to saiddownflow conduit, whereby when said conduits are at difierenttemperatures the escape of gas will tend'to be mainly through the outletof whichever conduit has the highest temperature.

8. The method of control of temperature in a refrigerated enclosure byevaporation of solidified carbon dioxide which comprises establishing arefrigerating source of solid carbon dioxide having desired modifiedmaximum normal rate of evaporation, said modification of the normal rateof evaporation of said carbon dioxide being effected by providing aconfining wall aflording predetermined protection against absorbing heatdirectly from anvarea being refrigerated while permitting access to thecarbon dioxide of air or air gas mixture, and controllably decreasingthe normal maximum rate as predetermined by controllably decreasingaccess of the air or air gas mixture to said solid by the amount andtightness of an insulating medium additionally and closely containingthe carbon dioxide within the space provided by the confining wall. 4

Signed, at New York, in the county of New York, and State of New York,this 20th

